Bells, Rockets, Dishwashers

For human beings, imagining a future world has never been a problem .

Future humans need to use technology to escape from the refrigerator and fly to other worlds, to use cats as "bombs" of robot worlds, to constantly pet cats to prevent explosions, from bloody and cruel duels to long and vast space journeys, from cyberpunk psychedelic to the spoofs of alternate history...

Of course, the extension of imagination is more or less able to find some shadows of reality - legend has it that as early as the 16th century, Wanhu began to try to use China's advanced fireworks technology to generate power, hoping to drive themselves to successfully fly, after a hundred years of exploration, today's mainland rocket "Fat Five" has been able to achieve take-off thrust of more than 1,000 tons, successfully lifting Tianwen-1, Chang'e-5 and the core capsule of the space station to space.

GIF | CCTV News

Bringing these "accessories" has added a lot of burden to the rocket, but if you look closely at the bottom of the rocket, you will find that there seem to be some extra parts, such as a few branches at the bottom of the rocket on the outside, like a bell-like device, it seems that it is just a stable base used to maintain a stable base before the rocket launch? but...... The oil price next to the community is already 9 yuan, can removing these "bells" reduce weight and save more valuable fuel?

The "bell" in front of you is not a bell

Take apart these "bells" and find that it has two large middle thin ends and a small waist! However, don't think that this is just for stabilization, this is the Laval nozzle of the rocket thruster, the key to the rocket's ability to go straight to space. Why not make the rocket thruster directly into a big and small one, just like a water pipe to nourish the water, but to make this bell shape?

The bell-shaped structure at the tail of the rocket | giphy.com

We need to know that the continuity theorem corresponding to the conservation of mass will be followed in the fluid flow process, that is, the flow of air and water into the cross-section in a unit time is equal to the flow rate flowing out of another section.

where: A represents the cross-sectional area of the flow pipe, v represents the flow rate of the airflow, and Ma represents the Mach number

From this formula, we can see that when less than Mach 1 (below the speed of sound), the cross-sectional area of the flow pipe is inversely proportional to the flow rate, that is, the flow tube shrinks and the flow rate increases; the flow pipe expands and the flow rate decreases. For example, when we squeeze the water pipe with our hands to nourish the water, it is artificially reduced the cross-sectional area of the water pipe mouth, if the water wants to ensure that the flow of water is equal to the inflow, it is bound to accelerate at the exit place, so that the flow is equal at both ends.

The laval tube has a middle throat structure that allows airflow to | from Ma1 youtuber mekanizmalar

But what about when the flow rate is directly increased to greater than Mach 1 (above the speed of sound)? To obtain this high-speed fluid, it is probably impossible for the water pipe to nourish the water, but the rocket thruster said that it was still ready for a fight! However, through the above formula, we can see that the coefficient of the formula becomes positive at the hypersonic speed, so the flow rate and the cross-sectional area of the flow pipe are just reversed, proportional to each other, that is to say, the flow rate will be reduced by trying to reduce the pipe.

It's all fluids, how can there be such a difference?

This is because in subsonic airflows, the relative change in density is smaller than the relative change in speed; in supersonic airflow, the relative change in density is greater than the relative change in speed.

Emm...... If you want to understand it in layman's terms, you can imagine that there is now a large group of students who have just left class and rushed downstairs from the classroom to the canteen, at this time, if the stairs change from 5 meters to 2 meters, then everyone will accelerate in order to hurry through; when everyone is fast enough to exceed Mach 1, the high-speed students themselves are already chaotic enough, if the stairs are narrowed from 2 meters to 1 meters, it will cause more serious congestion. But if you widen the staircase back to 5 meters at Mach 1, more people can pass through the space and the speed is released more.

The channel is opened to increase the flow rate by | giphy.com

For the past few hundred years, humans have been focusing on scenes below Mach 1, so it is difficult to artificially create supersonic speeds.

Based on this discovery, De-Laval invented the Laval tube, the base in the shape of a gourd, in 1883. Through the principle of first shrinking and then expanding, it will speed up the subsonic airflow first, and then continue to speed up the hypersonic airflow to reach a higher level and release super energy.

Not only can it "fly" the Laval tube

Based on this speed advantage, Laval tubes are also widely used in today's industrial fields.

The airflow crusher can accelerate the compressed air through the Laval nozzle into subsonic or supersonic airflow, and the jet of the spray drives the material to make high-speed movements, so that the material collides, friction and shear and crushes, not loose sand is better than loose sand.

In the converter steelmaking system, the Laval nozzle converts the pressure of oxygen into kinetic energy, the flow rate reaches the speed of sound at the throat, and in the expansion section, the pressure of oxygen can continue to be converted into kinetic energy, thereby obtaining a supersonic oxygen flow.

Vacuum suction glass requires a Laval tube | giphy.com

The Laval tube not only produces air, but also inhales. In environments that require vacuum, such as handling fragile glass, precision solar panels, and opening ultra-thin plastic films, the high-speed jets spewed out by the Laval tube can suck away the gas in the negative pressure chamber, forming a negative pressure that can quickly create a vacuum environment and facilitate industrial processing.

Space thoughts under the kitchen

Advanced aerospace technology is often for better civilian use, so as to serve the public life, kitchen expert - Fang Tai this time borrowed the rocket thruster's Laval tube idea, the dishwasher spray arm carried out a large wave of structural technology upgrades, to see how it and the rocket shoulder to shoulder ~ ~

The sugar cubes that are placed in the sink in the video are eroded by the water flow at a very fast speed, and the schoolchildren do not take it in their mouths so quickly... What is silently working behind it?

Cavitation of the bubble water stream erodes the sugar cube

We noticed that the left pipe produced a large number of bubbles without contact with air, and the bubbles were not produced out of thin air, but from high-speed water flow - water will form a violent vortex at the contraction and expansion of the channel, the flow rate in the center of the vortex is very large, according to Bernoulli's equation, the greater the flow rate of water, the smaller its static pressure, when this static pressure is less than the saturated vapor pressure of the water at this temperature, the water will vaporize to form bubbles, which is the famous cavitation phenomenon.

FangTai has previously passed through the Venturi tube structure, so that the dishwasher cleaning water flow has produced cavitation phenomenon, when the bubbles burst on the surface of the stain, it has formed countless small compression shock waves, playing an above-average efficient cleaning effect.

Lots of cavitation bubbles

But Fangtai did not stop at the original cleaning effect, this time taking inspiration from the Laval tube structure of the rocket injector to create a new generation of high-energy bubble washing nozzles: some "big moves" were made in the internal structure of the spray arm - adjusting the runner shape and aperture of the nozzle, as well as the size of the self-aspirating air hole to a reasonable proportion of water vapor mixing, thereby increasing the jet head by more than 20%.

Under the same experimental conditions, we made three kinds of structural tubes, namely ordinary straight pipe, Fang Taiyuan high-energy bubble washing nozzle, and Fangtai new generation of high-energy bubble washing nozzle, and compared them in terms of water flow rate and sugar erosion effect, and observed and recorded with a high-speed camera, and the results were as follows:

Three-tube comparison experiment: water flow rate

Three-tube comparison experiment: sugar cube erosion effect

The test shows that in the flow channel, Fangtai, which borrows the structural idea of the rocket Laval tube, borrows the new generation of high-energy bubble washing nozzles, because the adjustment and optimization of the structure can greatly improve the cavitation effect while increasing the flow rate, bringing a more obvious erosion effect, and bringing a strong cleaning ability of "doubling and doubling" to the dishwasher.

You may be worried about thrifty family management: how much water and electricity does such a high-speed water flow consume? Good design is actually planning for you to be exquisite. In order to solve the energy loss of the water flow vortex, fangtai dishwasher adopts the digital twin technology used to monitor the operation situation of the ship in the aerospace field in the research and development process, establishes a complete set of models of the internal flow channel of the pump and the spray arm, and cooperates with the built-in sensors to calculate the water flow efficiency by constantly adjusting the parameters of each position, so as to obtain the optimal cleaning and cleaning effect. Washing dishes is a small matter, and your family also needs an efficiency expert!

Digital twin technology to empower optimal cleaning results

The launch of the Long March 8 rocket touched the hearts of the people of the whole country, and at the moment when the thruster spewed flames, the whole country rejoiced, and the strength of people also seemed incomparably small. However, when cutting-edge fluid technology is applied to more ordinary people's homes, when the dishwashing experience of thousands of households is related to a certain artificial "star" in the distant starry sky, the spark of the collision of scientific and technological power and human wisdom has been infinitely expanded.

It is better to let Fang Tai dishwasher complete the daily tedious work for you immediately, and leave more time to look up at the stars

Produced by the Ministry of Commercial Technology Communication